Edit: I did write output file

I've been doing some past USACO Gold problems lately, but I have met some troubles regarding submission. Although my program outputs the correct answer, it keeps telling me that the answer is incorrect. I've met these kind of troubles before, so I thought its just a format issue. But no matter how I adjust the way I output the answer, it doesn't work.

For example, I have tried cout << ans << "\n"; cout << ans << endl; cout << ans << " "; cout << ans; but non of them works.

Here are two screenshots:

Can someone please help me with that? I just don't want to run into these kind of troubles during real contest lol. Thanks!